Irukandji syndrome

Irukandji syndrome is a seldom fatal, but nevertheless painful condition induced by the sting of Carukia barnesi, the Irukandji jellyfish, and other cubozoans.^[1] The condition was given its name in 1952 by Hugo Flecker, after the Aboriginal Irukandji people who live in Palm Cove, north of Cairns, where stings are quite frequent.^[2]

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Early experience

In 1964, Dr. Jack Barnes confirmed the cause of the syndrome to be due to the small box-shaped Irukandji jellyfish. In order to prove that the jellyfish was the cause of the syndrome, he captured one and deliberately stung himself, his son, and a local lifeguard, and observed the symptoms^[3] It is suspected that other Cubozoa can cause Irukandji syndrome,^[4] but only seven jellyfish have been positively identified (Carukia barnesi, Alatina nr mordens, Carybdea alata, Malo maxima, Carybdea xaymacana, an as-yet unnamed ‘fire jelly’, and 1 other unnamed species).^[5][1]

Toxicity

When properly treated a single sting is normally not fatal; however, two people in Australia are believed to have died from Irukandji stings^[6] which has greatly increased public awareness of Irukandji syndrome. It is unknown how many other deaths from Irukandji syndrome have been wrongly attributed to other causes.^[6] The exact mechanism of action of Irukandji venom is unknown. It has been suggested that catecholamine excess may be an underlying mechanism in severe Irukandji syndrome.^[7] Animal studies appear to confirm a relationship between envenoming and an increase in circulating noradrenaline and adrenaline.^[8]

Symptoms

Most stings occur during the summer wet season in December-January. The sting itself is often barely noticed, but the symptoms gradually become more intense in the following 5 to 120 minutes (30 minutes on average). Irukandji syndrome includes an array of systemic symptoms including severe headache, backache, muscle pains, chest and abdominal pain, nausea and vomiting, sweating, anxiety, hypertension, and pulmonary edema.^[3][9] Symptoms generally abate in 4 to 30 hours, but may take up to a week to resolve completely.^[4]

Treatment

Similarly to other box jellyfish, first aid consists of flushing the area with vinegar to neutralize the tentacle stinging apparatus. There is no antivenom; treatment is largely supportive, with analgesia being the mainstay of management. Antihistamines may be of benefit for pain relief,^[10] but most cases require intravenous opioid analgesia. Fentanyl or morphine are usually chosen. Pethidine (aka meperidine in U.S. (Demerol)) should be avoided, as large doses are often required for pain relief and in this situation significant adverse effects from the pethidine metabolite norpethidine may occur.^[11]

Magnesium sulfate has been proposed as a treatment for Irukandji syndrome after the successful treatment of one patient.^[12] Early evidence suggested a benefit;^[13] however, one series of 3 patients failed to show any improvement with magnesium with the author reiterating magnesium's experimental status for Irukandji syndrome.^[14]

Geographic distribution

Reports of Irukandji syndrome have come from Australia, Hawaii, Florida, French West Indies, Bonaire, the Caribbean, Timor Leste and Papua New Guinea.^[3] It is presumed that cubozoan species other than Carukia barnesi are responsible for envenomations outside Australia.^[1]

Media demonstrations

The severity of the pain from an Irukandji jellyfish sting is apparent in the 2005 Discovery Channel documentary Killer Jellyfish on Carukia barnesi, when two Australian researchers (Jamie Seymour and Teresa Carrette) are stung. Even under the "maximum dose of morphine" Teresa remarked that she "wished she could rip her skin off", and is later seen writhing uncontrollably from the pain, while lying on her hospital bed. In a particularly disturbing shot, we see Teresa's feet contorting and digging into the bed. When the camera pulls out to a wide shot, she is rubbing her face, her body is contorting in agony, and her legs are rapidly sliding and kicking around on the bed. Jamie, at his worst, is also seen writhing in pain, curled up in a ball and barely able to speak. Jamie said he wished that he was stung by Chironex fleckeri instead since "the pain goes away in 20 minutes or you die".

Another recent program that aired on the Discovery Channel entitled Stings, Fangs and Spines featured a 20 minute spot on Irukandji Syndrome. In the segment, a young Australian woman was stung and developed a severe case of Irukandji syndrome. In a testament to the severity of pain involved, a re-enactment (featuring the actual victim portraying herself) shows her screaming and violently thrashing around on the hospital bed in an almost convulsive state, for the bulk of the segment. She later commented that this unbearable pain lasted for hours, and added that "I didn't think it was possible for anyone to endure that level of pain without turning into a vegetable".